This research focuses on the ability to generate mental images, or "see with the mind's eye." The first goal of the research is to learn about the organization and neural localization of image generation by studying the image generation abilities of brain-damaged patients. The specific questions addressed are: What are the separable components of image generation ability? What parts of the brain are critical for these components? The second goal of the research proposed here is to clarify the nature of the underlying cognitive deficit in certain types of visual/spatial disorders that follow brain-damage. This aspect of the research involves testing the hypothesis that a loss of imagery ability underlies the following clinically relevant visual/spatial disorders: Visual retention deficits, visuo-constructive deficits, and topographic disorientation. The methodology consists of administering a set of tasks designed to selectively tap different components and type of image generation (detailed visual, "sheletal" visual, and auditory) to a variety of patients selected either for lesion location (right, left, anterior, posterior) or visual/spatial deficit (topographic disorientation, constructional apraxia, visual retention deficit). Degree of association or dissociation between different types of image generation will reveal the organization of image generation. Relations between image generation deficit and lesion location will reveal critical brain areas for image generation (including testing a specific hypothesis about the localization of visual image generation). Correlations between clinical visual/spatial deficits and image generation deficits will test hypotheses about the role of imagery deficits in clinically relevant disorders.